android studio 新建一个项目，却出现Design editor is unavailable until after a successful project sync
waiting for build to finish
点击工具栏File -> sync project with Gradle Files
结果build 失败，系统提示：Failed to find Build Tools revision 28.0.2
在项目根目录下local.properties文件中看到：
sdk.dir=C\:\\Users\\Gouge Penguins\\AppData\\Local\\Android\\Sdk
于是到C:\Users\Gouge Penguins\AppData\Local\Android\Sdk下寻找sdk，该目录下ls看到：
build-tools/ emulator/ extras/ patcher/ platforms/ platform-tools/ sources/ system-images/ tools/
于是cd build-tools看到
28.0.3/
Android studio需要的build tool和sdk中的版本不一致，于是在Failed to find Build Tools revision 28.0.2 有install Build Tools revision 28.0.2，点击即可下载